Current automotive seats have become extremely complex in construction and this trend is continuing. Thus current automotive seats are routinely expected to provide for a whole variety of adjustments aimed at enhancing occupant comfort and safety. These adjustments include forward and backwards movement to enable the position of the seat on the longitudinal axis of the vehicle to be adjusted, and upward and downward adjustment to enable the position of the seat on the vertical axis of the vehicle to be adjusted. The forward and backward adjustment in turn enables the position of the front seats with respect to both the dashboard and the rear seats to be adjusted. The upward and downward adjustment in turn enables the height of seats with respect to the floor and roof of the vehicle to be adjusted. Where the seat in question is the driver's seat these adjustments enhance the ability of the driver to select the most comfortable and favourable driving position particularly with respect to the steering wheel. Other adjustments may provide for the adjustment of lumbar support, for the adjustment of headrests and for the adjustment of the squab part of the vehicle seat with respect to the seat part. This latter adjustment is usually a pivotal adjustment enabling the squab part to rotate or pivot with respect to the seat part. The mechanisms inherent in the provisions of all of these adjustments impart a certain degree of play or flexibility to a seat which would not be there without them. Whilst this is necessary under normal operating conditions it may be less desirable under impact conditions. It is an object of the invention to remove or mitigate this.